defluxing using spray

[linuxworks]

how safe is a deflux spray like this:

I've been using this for a few months now and it works great. but I worry about which components might have problems - such as trimmer pots, transistors on heatsinks (thermal gray pads), electro caps and even onboard relays.

my guess is that I should assemble all the parts that would be fully and completely sealed and then deflux. after that, use a 'no clean' solder when attaching the final parts (relays, pots, trimmers).

what do people do? it would be nice to just finish the whole board, do a light spray on the top and a heavier spray on the bottom and brush it (or canned-air dry it) but I do worry about the chemical getting into the electro caps and especially the multiturn cermet trimmers.

 

[tomb]

Quote:

Originally Posted by linuxworks /img/forum/go_quote.gif how safe is a deflux spray like this: <img]http://www.all-spec.com/images/1621-10s.gif[/img> I've been using this for a few months now and it works great. but I worry about which components might have problems - such as trimmer pots, transistors on heatsinks (thermal gray pads), electro caps and even onboard relays. my guess is that I should assemble all the parts that would be fully and completely sealed and then deflux. after that, use a 'no clean' solder when attaching the final parts (relays, pots, trimmers). what do people do? it would be nice to just finish the whole board, do a light spray on the top and a heavier spray on the bottom and brush it (or canned-air dry it) but I do worry about the chemical getting into the electro caps and especially the multiturn cermet trimmers.

Depends on how much spray you use. Typically, caps and such are solvent-resistant, meaning not immersion-proof. A volume pot is perhaps the only issue. Many, such as the RK27, have greased shafts and your defluxing can remove that, changing the entire "feel" of the volume pot.

I prefer the straight alcohol (91% from Walmart) with a toothbrush - and I've used the stuff you've pictured. Nasty smelling and a mess, IMHO. With alcohol you can do the entire board once finished - just as you suggest. You can even use smaller toothbrushes and cleanup spots on the topside, which by and large, should be pretty clean. The bottom gets a half-dozen thick coatings with the toothbrush on a large board, with a good absorbent paper towel inbetween. The paper towel is important, IMHO, because that's the only thing that actually removes the flux - and the yellowish-brown color on the paper towel is proof.

FYI - the volume pot, or any part on the topside of the board, is not an issue using this method.

Like many things such as this, I'm sure we all have our own methods. This one works for me, though.

 

[linuxworks]

I've tried alcohol but it does not dissolve as fast or as easy as that spray.

the can of spray is $12, though ;(

so, even with trimmers on a pcb, you'd still use something liquid like alcohol?

 

[adamus]

certianly wouldnt submerge, but i would still attack the underside with a toothbrush. some electrolytics arent sealed.

 

[linuxworks]

the thing I hate about using brushes is that sometimes you can remove some of the green resist/mask. some boards don't have a really strong resist layer.

one thing I like about that spray is that with the nozzle, you can accurate aim for parts of the board to flush and you don't douse the board with the spray method.

if you don't mind using extra spray, you can simply angle the board, hit it with spray and the force of the spray, the chemical action and gravity simply let the flux drip off. no towels needed. but it is somewhat wasteful of that canned stuff.

so far I've been giving the top a light point-focused bit of spraying, drying it with a paper towel and then hitting the bottom of the board a few times and letting it drip dry, pretty much.

the one thing I like about the defluxed board is that its now easy to SEE if you have shorts or bridges. I'm not at all convinced that audio frequencies NEED defluxing but it really does make for an easier pre-power-up inspection.

 

[digger945]

Glad you started this thread, I've been thinking about this for a while now and wondered if there was a better way than alcohol and scrubbing/rubbing. Does it leave any film on the pcb?
I just started using Kester #951 Low solids/ No clean flux pen and so far it's quite a bit cleaner than the #186 Type RMA flux pen.

 

[linuxworks]

I use the same brand 'no-clean flux pen' (odd since it does seem to need cleaning, at least I think so)

it dispenses a liquid and it does make the solder flow easier. but it leaves 'water spots' (sort of) behind that I do want to clean up.

regular alcohol cleans that up easily, no need for spray.

the spray stuff is useful to losen the flux from cored solder (and this pen-based flux, too) and then the pressure of the spray just forces it off the board. I spray for 3 seconds at a time, then let it drip a bit and maybe even alternate with canned air.

if I know all parts are fully sealed (really know this) then I might run hot water in the sink and alternate with sprays and then hot water washes. then some canned air at the end to fully dry it off. sort of like a mini car wash (lol) for pc boards.

I once worked at a very small board assembly shop as a teenager (back in the 70's). we used acid flux (!!) which was some liquid red stuff, very loose (not thick at all) and we'd paint it over some areas, do manual solder iron touch-ups, then when enough were done, we'd take the rack over to the sink and treat them like dishes! I'm not kidding you, we'd have soapy water (or some kind of stuff) and we'd brush the top and bottom, rinse, blow dry and put them on a dish rack. it cracked me up, it was so funny to see, but apparently that system worked well for the guy and had been doing it this way a long time. they wave-soldered the boards but needed some manual touch-ups (what I did for that summer job) before they were ready to be QC'd and shipped.

I have not seen acid flux used since that time but I do like to 'wash and dry' the boards sort of like I learned many years ago. just not quite so aggressive!

 

[tomb]

Quote:

Originally Posted by linuxworks /img/forum/go_quote.gif the thing I hate about using brushes is that sometimes you can remove some of the green resist/mask. some boards don't have a really strong resist layer.

Well, we're talking toothbrushes here, not wire brushes - never had a problem with this, but then we only use quality boards.

Quote:

one thing I like about that spray is that with the nozzle, you can accurate aim for parts of the board to flush and you don't douse the board with the spray method. if you don't mind using extra spray, you can simply angle the board, hit it with spray and the force of the spray, the chemical action and gravity simply let the flux drip off. no towels needed. but it is somewhat wasteful of that canned stuff. so far I've been giving the top a light point-focused bit of spraying, drying it with a paper towel and then hitting the bottom of the board a few times and letting it drip dry, pretty much. the one thing I like about the defluxed board is that its now easy to SEE if you have shorts or bridges. I'm not at all convinced that audio frequencies NEED defluxing but it really does make for an easier pre-power-up inspection.

It's all part of doing quality work.

However, electrical issues become reality over time if the flux is not cleaned up. When you see electronics that are many years old, but not properly cleaned of flux - it's easy to see how it would become conductive.

You've noted the issues about the spray flux. The thing is, it's just as easy to hold the board up and let it drip if you applied the alcohol with a toothbrush. At 90 cents a quart at WalMart and without the dangerous fumes of the other stuff, the choice has been clear with me. Again, there's no right or wrong, necessarily, as long as it gets cleaned.

Although, I saw one guy post in a thread like this (there have been several) to use soap and water. I'd draw the line at that one.

EDIT: Must've been the acid flux crowd.

 

[linuxworks]

with acid flux, its not an option - you MUST wash it off.

I thought I had saved some of that liquid but I can't find it anymore. maybe that's a good thing

I do still have some tacky rosen non-acid flux from that same shop. its dark, like maple syrup and if you paint it on a pc board it will actually hold SMD parts while you solder them. neat stuff. when my supply of that is gone, its gone forever and I have no idea what was even in it. its what we used when we didn't want (or could not) do the 'full wash' after a solder touch-up.

I saved some of that rosin liquid flux in a baby food jar - which was the common container of use at the time (lol)

 

[amb]

I use the spray flux remover all the time, and it works very well, but the chemical is nasty, so avoid inhaling the fumes. Also, certain electrolytic caps' printed markings could be dissolved by it (e.g., Panasonic TS-HA series). I use this stuff carefully on any board with these caps, or board-mounted pots (covering them if necessary), and not to use excessive amounts.

 

[linuxworks]

I would think that a can of spray that was purpose-designed for defluxing would deal well enough with typical rubbers and plastics that you'd find on the parts. scary to hear that this stuff has ruined things, even if only cosmetically.

I used to use datak brand dry transfer lettering ('rub-on letters') and they used to make a spray, 'datak coat', that was not reactant with the lettering. of course I didn't know about that and used some clear nail polish, thinking it would be 'just as good' and of course it wasn't; the lettering would lift off and even bubble in the combined chemistry. any project that I did from that era would have distorted wavy lettering under the clear sealant

then I finally got some of the proper spray coat and the chemical reaction stopped happening.

I've had lettering come off on the pcm2702 dac chip when I used a toothbrush and alcohol. I lost the prized BB logo (lol) when I overcleaned that bantam dac board. after that, I tried to avoid using brushes and tried to go with a touchless style system.

 

[digger945]

So maybe it might not be too bad to just spray some of this stuff in a cup or something and use it with a Q-tip or brush. I guess it doesn't matter much where you clean with the spray can stuff as it probably evaporated quickly.
Has anyone used the Electronics/Contact cleaner stuff in the red can, I saw some at Ace Hardware and other places?

I know what you mean by the no clean stuff leaving what looks like water spots.

 

[MisterX]

Quote:

just spray some of this stuff in a cup or something and use it with a Q-tip

Or better yet...

IC-POP-ESD-50 - R&R Lotion Swabs Alcohol Filled 50/Pak - IC-POP-ESD-50

 

[jacc1234]

Those look great MisterX! I will probably be picking some up. On another not it does not seem like many people bother with the 99.9% pure Isopropyl. I kept getting a white residue with store bought stuff and ended up buying some from MG chem and I like it a lot. Its not super cheap but at $12 a L, I can manage.

 

[Iniamyen]

I use the 99.99% isopropyl that I get at Fry's for like $10 for a big bottle. Not the best deal but I don't know where else to get it.

I use a toothbrush, but I don't scrub the bottom of the board too hard. Instead, I try to slowly dissolve the flux in the alcohol and move it to one side of the board with gentle strokes of the brush. After the bottom of the board is nice and dripping with the alcohol, I use canned air to blow it off, removing the flux with it. I can get most of the flux off the board only repeating this 3 or 4 times. Some alcohol will splash onto components, but hardly enough to worry about. Personally, I'd be much more afraid of the nasty flux remover spray getting on my components.